Topic 3 - NERVOUS SYSTEM I (Neuronal Physiology - RMP)

Question 1

resting membrane potential (RMP)

• what is membrane potential?
• approximatley equal to?

Answer 1

• at rest (non stimulated) a charge difference (potential difference) exists just across the cell membrane = membrane potential
• approximately equal to -70 mV = 70 mV more negative than outside

Question 2

factors establishing RMP

A

• ATPase - not a ______
  
  • is the Na⁺/K⁺ - ATPase passive transport or active transport and why?
• what are the 2 effects?

Answer 2

• Na⁺/K⁺ - ATPase pump - not a channel
  
  • active transport because both ions are pumped against their concentration gradients
  • effects:
    
    • maintains concentration gradients of Na⁺ and K⁺
    • contributes a little (a few mV) to RMP (pumping more positive ions out than in)

Question 3

factors establishing RMP

B

Answer 3

large, negatively charged organic ions inside cell

example: proteins - cannot cross membrane

Question 4

factors establishing RMP

C

Answer 4

more non-gated K⁺ channels than non-gated Na⁺ channels.

(membrane is more permeable to K⁺ than Na⁺ at rest. Therefore, K⁺ is a major determinant of RMP)

Question 5

factors establishing RMP

C) …therefore, K+ is a major determinant of RMP

Step 1

1. ???
2. unlike charges attract and K+ diffusion slows as inside becomes increasingly negative
3. Na+ diffusion into cell increases due to increasing attraction to negative cell interior
4. Until -70 mV is reached, positive out (K+) is greater than positive in (Na+) - greater K+ permeability
5. at -70 mV, the amount of positive (K+) moving out equals the amount of negative (Na+) moving in
6. therefore, the net movement of charge (ions) is 0 (equal in both directions: RMP = -70 mV)

Answer 5

K+ diffuses out of cell concentration gradient. therefore, cell loses positive charge (inside becomes more negative)

Question 6

factors establishing RMP

C) …therefore, K+ is a major determinant of RMP

Step 2

1. K+ diffuses out of cell concentration gradient. therefore, cell loses positive charge (inside becomes more negative)
2. ???
3. Na+ diffusion into cell increases due to increasing attraction to negative cell interior
4. Until -70 mV is reached, positive out (K+) is greater than positive in (Na+) - greater K+ permeability
5. at -70 mV, the amount of positive (K+) moving out equals the amount of negative (Na+) moving in
6. therefore, the net movement of charge (ions) is 0 (equal in both directions: RMP = -70 mV)

Answer 6

unlike charges attract and K+ diffusion slows as inside becomes increasingly negative

Question 7

factors establishing RMP

C) …therefore, K+ is a major determinant of RMP

Step 3

1. K+ diffuses out of cell concentration gradient. therefore, cell loses positive charge (inside becomes more negative)
2. unlike charges attract and Potassium diffusion slows as inside becomes increasingly negative
3. ???
4. Until -70 mV is reached, Potassium out is greater than Sodium in - greater K+ permeability
5. at -70 mV, the amount of Potassium moving out equals the amount of negative sodium moving in
6. therefore, the net movement of charge (ions) is 0 (equal in both directions: RMP = -70 mV)

Answer 7

Na+ diffusion into cell increases due to increasing attraction to negative cell interior

Question 8

factors establishing RMP

C) …therefore, K+ is a major determinant of RMP

Step 4

1. K+ diffuses out of cell concentration gradient. therefore, cell loses positive charge (inside becomes more negative)
2. unlike charges attract and K+ diffusion slows as inside becomes increasingly negative
3. Na+ diffusion into cell increases due to increasing attraction to negative cell interior
4. ???
5. at -70 mV, the amount of positive (K+) moving out equals the amount of negative (Na+) moving in
6. therefore, the net movement of charge (ions) is 0 (equal in both directions: RMP = -70 mV)

Answer 8

Until -70 mV is reached, positive out (K+) is greater than positive in (Na+) - greater K+ permeability

Question 9

factors establishing RMP

C) …therefore, K+ is a major determinant of RMP

Step 5

1. K+ diffuses out of cell concentration gradient. therefore, cell loses positive charge (inside becomes more negative)
2. unlike charges attract and K+ diffusion slows as inside becomes increasingly negative
3. Na+ diffusion into cell increases due to increasing attraction to negative cell interior
4. Until -70 mV is reached, positive out (K+) is greater than positive in (Na+) - greater K+ permeability
5. ???
6. therefore, the net movement of charge (ions) is 0 (equal in both directions: RMP = -70 mV)

Answer 9

at -70 mV, the amount of positive (K+) moving out equals the amount of negative (Na+) moving in

Question 10

factors establishing RMP

C) …therefore, K+ is a major determinant of RMP

Step 6

1. K+ diffuses out of cell concentration gradient. therefore, cell loses positive charge (inside becomes more negative)
2. unlike charges attract and K+ diffusion slows as inside becomes increasingly negative
3. Na+ diffusion into cell increases due to increasing attraction to negative cell interior
4. Until -70 mV is reached, positive out (K+) is greater than positive in (Na+) - greater K+ permeability
5. at -70 mV, the amount of positive (K+) moving out equals the amount of negative (Na+) moving in
6. ???

Answer 10

therefore, the net movement of charge (ions) is 0 (equal in both directions: RMP = -70 mV)